Automatic pressure-relief mechanism for railway air-brakes.



No. 662,476. Patented Nov. 27, I900. 8. L. TERRY. AUTOMATIC PRESSURERELIEF MECHANISM FORRAILWAY AIR BRAKES.

(Applicmzimra filed Oct. 4. 1899.)

2 Shuts-Sheet I.

(No Model) Milli,

Wi'h essas No. 662,476. Patented Nov. 27, I900.

S. L. TERRY.

AUTOMATIC PRESSURE RELIEF MECHANISM FOR RAILWAY AIR BRAKES.

(Application filed Oct. 4,1899. (No Model.)

2 Shaets8heot 2.

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UNITE STATES rrrcn.

SAMUEL L. TERRY, OF CHICAGO, ILLINOIS, ASSIGNOR OF TWELVE TWENTY FIFTHSTO J. \V. MAS'IIN, OF DENVER, COLORADO, AND GEORGE C.

MASTIN, OF OAK PARK, ILLINOIS.

AUTOMATIC PRESSURE-RELIEF MECHANISM FOR RAILWAY AIR-BRAKES.

SPECIFICATION forming part of Letters Patent No. 662,476, dated November27, 1900.

Application filed October 4, 1299.

To aZZ whom it may concern: 4 Be it known that I, SAMUEL L. TERRY, aciti zen of the United States, residing at No. 4,731

State street, in the city of Chicago, in the State of Illinois, haveinvented a new and useful Automatic Pressure-Relief Mechanism forRailway Air-Brakes, of which the following is a specification.

Myinvention relates to an automatic pressure-relief mechanism forrailway air-brakes or, as it may be termed, a device for preventin gflat wheels'on railway-cars and primarily the invention is designed torelease the airpressure in the pistoncylinder of the brake mechanismwhen the brakes are applied to retard or to arrest the train.

A further object of the invention is to relieve the brake-pressure andprevent flattening a car-wheel when the latter ceases to turn for anycause whatever in the service or in the running of the train.

A further object of the invention is to so arrange the relief mechanismthat it will not open the relief valve or valves when the train isstanding at rest at a station or other place and the brakes areundergoing the usual test preiiminaryto starting the train in service.

A further object is to provide a relief mechanism which shall be whollyautomatic, simple and reliable in service, will permit inspection andrepairs of the several elements,- and will enable the brake to beapplied by hand with ease and freedom.

With these ends in view the invention consistsin the com bination,with abrake-cylinder of an ordinary air-brake mechanism, of a relief-pipehaving a series of relief-valves normally closed and located adjacent toeach of the series of wheel-axles of a railway-car, a trip mechanismcontrolled by each axle and adapted to actuate the relief-valve whenthewheel or axle ceases to turn, and means actuated by the brakemechanism to preliminarily move an elementof a relief-valve in the pathofthe trip mechanism.

The invention further consists in the novel combination of mechanismsand in the construction and arrangement of the various parts forservice, which will be hereinafter fully described and claimed.

Serial No. 732,529. (No model.)

To enable others to understand the invention, I haveillustrated apreferred embodiment thereof in the accompanying drawings, forming apart of this specification, in which- Figure 1 is a partial plan View ofan ordinary brake mechanism with my improved pressure-relief mechanismassociated operatively therewith. Fig. 2 is a sectional elevation in theplane of a car-wheel axle, illustrat- 6o ing the improved trip mechanismand a relief-valve in active relation to the axle, the trip mechanismbeing shown in its lowered position to engage with the relief-valve whenthe axle ceases to turn for any cause. Fig. 3 is a sectional elevationin a plane at right angles to the car-Wheel axle, showing the parts ofFig. 2 in their working positions when the axle is in motion. Fig. 4 isan enlarged sectional elevation of the parts of the trip mech- 7o anismand the relief-valve in the position shown by Fig. 2. Fig. 5 is anenlarged detail perspective view of the trip-mechanism casing removedfrom the axle. Fig. 6 is a detail perspective view of the weighted yokeand arm forming one element of the wheel-driven trip mechanism. Fig. 7is a detail sectional view, on an enlarged scale, of one of therelief-valves. Fig. 8 is a detail sectional view illustrating a part ofthe ordinary piston brake-cylinder,showing the sleeve con nectionbetween the brake-piston and the relief-valveactuating rod. Fig. 9 is adetail of the cam for actuating the valve lever or arm previous toopening the valve by the trip mechanism.

The same numerals of reference are used to indicate like andcorresponding parts in each of the several figures of the drawings.

Referring more particularly to Fig. 1, the numeral 10 is used todesignate the ordinary 9o train-pipe of an air-brake mechanism whichincludes the pressure-reservoir 11, the latter having operativeconnection through a triple valve and branch pipe 12 with thetrain-pipe.

As is usual with railwayZair-brakes a piston- 5 cylinder 13 is connectedoperatively with the pressure-reservoir by the triple valve, and thisbrake piston-cylinder actuates a brakelever 14, the latter havingoperative connections, as 145, with the brake-beams which connection thebrake piston-cylinder is pcculiarly constructed for its piston-to have alimited travel independently of the pistonrod for the purpose ofproperly actuating the relief-valve rod. The piston 16 of thebrakecylinder is provided with an elongated sleeve 17, which playsthrough the usual stuffingbox, and said brake-piston is returned to itsnormal position on release of the brake-pressure by a spring 16*, as isusual. This sleeve is formed with an upwardly-extending arm 18, thelatter adapted to be made fast with an endwise-movable rod which carriescam devices in active relation to a movable element on the relief-valve,as will hereinafter appear. The piston-rod 19 is loosely fitted in thepiston-sleeve 17, so that the piston-rod is capable of a limitedmovement independently of the piston-sleeve on the operation of theusual hand appliances for the application of the brake, and between thepiston and the end of the piston-rod is interposed a bearingball 20,which minimizes the friction on the end of the piston-rod, the outer endof said rod being attached pivotally at 20 to the brake-lever.

- wheels take up the motion of the axle.

Each axle 21 of the car is provided with bearing-collars 21, and on thisaxle is mounted the casing'22 for the trip mechanism, said tripmechanism being housed or contained within the casing in active relationto the axle. The casing 22 is divided transversely in a vertical planefor ready application to the axle, said casing being of cast-metal or ofstamped sheet-metal construction and its members being bolted orotherwise firmly united together. The sectional casing 22 is sustainedloosely on the axle by means of an idle spindle 23, having the wheels orrolls 24, said spindle beingjournaled in the upper part of the casingand above the axle for the rolls 24 thereon to ride-upon the collars 21of the axle, whereby the casing is loosely supported on the axle and isprevented from displacement thereon, because the spindle and its Thecasing is provided in its opposite sides with thecoincidentaxle-openings25, which loosely receive the axle, and said casing isfurthermoreprovided. with the arc-shaped slots or guideways 25 Theseguideways are concentric with the axis of the axle-opening; but in lieuof making the guideways in the form of slots they may be formed bygrooves produced in the opposing faces ofthe sidewalls.

(See Fig. 4.) The casing is retained in position on the axle by means ofa guide-hanger 26, which is connected slidably with a part of thecar-truck, so as to permit of the necessary vibration or play, suchslidable connection being effected by means of a slide 27, fitting in aguideway 28. The hanger 26 has a flanged or enlarged foot 26 which isbolted firmly to the upper side of the casing 22, While the slide 27 isconfined in the guideway 28, so as to move freely in a verticaldirection, but is prevented from moving laterally in either direction,the guideway being fastened firmly to a beam of the car-truck, as shownby Figs. 2 and 3.

The trip mechanism for the operation of the relief-valve is combinedwith each axle of the car in a manner to release the air-pressure in thebrake mechanism should the wheels on that particular axle cease to turnor rotate for any reason whatever-such, for example, as the applicationof the brake-shoes under excessive pressure-whereby I am able to attainthe prime object of this invention-t'. 6., to obviate the formation offiat surfaces on the car-wheeh One element of the trip mechanism is amaster-gear 29, which may be of sectional construction adapted forreadyapplication to the axle, as shown by Fig. 4, or said master-gearmay be solid and secured in any suitable Way to the axle. Anotherelement of the trip mechanism is a spindle 30, which is provided at itsends with the wheels or rollers 30, the latter fitting loosely in theareshaped guideways 25*, so as to loosely support the spindle in placeand permit it totravel freely in the casing under certain conditionsandinapath concentric with the axle 21. This spindle is connectedoperatively with the axle by means of a gear 31, which meshes with themaster-gear 29,whereby on the rotation of the axle when the car is inmotion the gear 31 and the spindle will be maintained in the elevatedposition shown by Fig. 3 and at the upward limit of the arc-shapedguideway on one side of the axle,th us withdrawing the trip mechanismfrom active relation to the reliefvalve. Another element of the tripmechanism is a yoke 32, which is loosely sleeved on the spindle betweenits supporting-wheels 30 and the gear 31, and this yoke is provided witha counterpoise or weight 33 and with a depend ing trip-arm 34, saidtrip-arm adapted to project through a slot 35, which is formed in thecurved bottom of the loosely-supported casing '33. When the car is inmotion and the axle is rotating, the frictional engagement of themaster-gear 29 with the gear 31 will elevate the counterpoised yoke andthe spindle within the casing 22 up to the upper extremity of thearc-shaped guideway on one side or the other of theaxle,accordin-g tothe direction in which the axle is turning; but as the spindle isrevolubly supported within the easing by its wheels 30 the motion of thegear 31 under the influence of the master-gear effects no other purposethan to hold the triparm away from the relief-valve, one positionpassing through a suitable casing 44, supof the trip mechanism when thuselevated being shown by Fig. 3. If the axle ceases to to tate for anycause whatever, the master-gear will of course stop, and thereby permitthe trip device to be lowered to the position shown by Figs. 2 and 4,owing to the weight or gravity of the counterpoise 33 on the yoke. Atthis stage in the operation the gear 31 is free to travel around a partof the toothed circumference of the stationary master-gear, while thespindle is directed by the guide- Way in its travel within the casing,the triparm 34 moving freely in the slot 35 until the trip devicereaches a position perpendicular with respect to the axis of thecar-axle. At this time the trip-arm is lowered into position to engagewith an arm of the relief-valve for the purpose of opening saidrelief-valve to reduce the pressure in the reservoir associated with thebrake-cylinder, provided, however, the relief-valve has a movableelement thereof disposed in the path of the trip mechanism preliminaryto the lowering of the trip mechanism to its operative position.

Under some circumstances I may employ a relief mechanism in connectionwith each car-wheel axle; but to reduce the number of parts, and therebysimplify the mechanism, a single brake-cylinder may be employed for eachcar, as usual, the brake mechanism shown by Fig. 1 being common to allthe axles on the car. Under this embodiment of the invention I employ asingle relief-pipe 36, which is arranged contiguous to the series oftrip devices which are in active relation to the series of car axles.This relief-pipe 36 has a branch connection 36 with the brakecylinder.In the relief-pipe 36 is interposed a series of valve-casings 37, one ofsaid casings being placed adjacent to each trip device and saidrelief-valve being shown in detail by Fig. 7 Within the valve-casing issliclably fitted the relief-valve 38, which is held normally to itsseat, so as to close the relief-port 39, by means of a spring 40. Thevalve is adapted to be forced from its seat, so as to open the portthrough the medium of a jointed or two-part valve-arm 41, one member ofwhich is in active relation to the valve-spindle, so as to operate onthe latter when the valve-arm is moved in one direction or the otherunder the influence or action of the trip mechanism. Normally thevalvearm is free from the spindle of the valve, so that the latter maybe closed by its spring, as shown by Fig. 7. The two parts of thevalve-operating arm are joined together, as at 42, and against the freemember of this valve-arm acts a spring 43 of any suitable character, thelatterserving to hold the valvearm in a condition Where it is normallyfree or out of the path of the trip mechanism and is interposed into thepath of a cam on a valve-actuating rod 44. This valve-actuating rod 44extends lengthwise of the car in close relation tothe relief-pipe 36,said rod on the casing 22.

ported on and below the casing 22 of the trip mechanism. Said rod 44 isfastened securely to the arm 18 of the piston-sleeve, so as to be movedendwise, by the brake-piston when the latter is actuated to apply orrelease the brakes, and this endwise-movable rod is fitted slidably inhangers 45, suitably secured to the car-trucks or a part of the caritself. A series of cams 46 are carried by this rod, so as to have alimited movement therewith, each cam being provided with africtionsleeve 47, which engages with the rod with sufficient frictionalcontact to move therewith except when arrested by suitable stops The camhas its frictionsleeve fitted on that part of the valve-rod which passesthrough the casing 44 so that the cam lies adjacent to the relief-valve,but is out of the path of the trip mechanism. This cam is provided withpins or studs 48, and the rod passes through stop-guides 49, dependingfrom the casing 22 within the casing 44 A movement of the valve-rod inone direction causes the cam to travel therewith until its pins or studsstrike one hanger, and a movement of the valve-rod in the otherdirection effects a like play of the cam until arrested by its studsimpinging against the other hanger, whereby the cam is capable of alimited movement between the stop guides or hangers 49. The free arm ofthe jointed valve-lever is interposed in the path of the cam by theaction of the spring 43, so that the valve arm or lever will be out ofthe way of the trip mechanism even though the latter be lowered to itsoperative position; but when the valve-rod is moved by the applicationof the brakes the cam serves to depress or move the valve-lever into thepath of the trip-arm, so that when the trip is lowered its arm 34 willstrike the valve-leverand open the valve against the tension of thespring.

The operation is as follows: The jointed valve'lever is held out of thepath of the triparm in the path of the cam. With the train at rest thebrake may be operated without changing the position of the lever or therelief-valve, because the axle 21 is not turning for the master-gear tolift the trip mechanism. Hence the trip-arm is lowered, as shown by Fig.4, and the rod 44 may be moved by the brake, it being necessary in thissystem that the lever of the relief-valve shall be interposed in thepath of the trip-arm before the latteris lowered. With the train runningthe brakes may be applied to retard the motion of the train or to arrestthe same, and under these conditions the automatic relief mechanismbecomes operative to release the pressure in the brake-cylinder on theapplication of the brakes and in the event of excessive application ofthe brake-shoe to the wheels on any one axle of the car for the purposeof preventing the formation of flat surfaces on the car-wheel. WVhen theaxles are rotating, the master-gears on several axles operate so thatism being shown in Fig. 3.

in the manner described for the elevation ofthe trip-arms out of thepath of the reliefvalve levers, the position of the trip mechan- Insetting the brakes a reduction of pressure is made in the train-pipeleading from themain reservoir on the locomotive, which causes theexcess of pressure in the auxiliary reservoir to force the piston of theordinary triple valve down, and thereby move the slide-valve down ofsaid triple valve, so as to allow the air in the auxiliary reservoir(now of greater pressure than that in the train-pipe) to pass directlyinto the brake-cylinder and apply the brakes. This is so well known thatI have not considered it necessary to show thecOnstruction of the triplevalve, and, as equally well known, when the pressure in the train-pipeis again increased above that in the auxiliary reservoir the piston inthe triple valve is forced up, mov ing the slide-valve toits formerposition, opening communication from the train-pipe to the auxiliaryreservoir, and permitting the air in the brake-cylinder to escape, thusreleasing the brakes. It sometimes happens, however, that when it issought in the ordinary manner to apply the brakes a wheel becomes lockedby the action of the brake shoes thereon, and it is the especial purposeof my invention to overcome this objection in order to overcomeflattening of the wheels. At the period of setting the brakes the piston16 actuates the sleeve 17, the arm 18, and the valve-rod 44, wherebysaid rod is moved in order to operate the cams in a manner to move thevalve-levers into the path of the trip devices, said actuation of thevalve-levers taking place at the period of initial movement of the brakemechanism so that the cams and valve-levers assume their proper workingpositions before the brakes are fully applied. Now should either axlebecome locked or cease to rotate, the master-gear 29 on the non-rotatingaxle will stop and the weight 33 of the trip will pull the lever to aposition below the axle, the gear 31 and the. spindle 30 of the triprotating freely during the downward travelof the weighted yoke. Thelever of the relief-valve having been interposed in the path of the tripby the valve-rod and the cam, the trip-arm 34 on the descent of the tripmechanism strikes against the valve-1ever and moves the valve to itsopen position, thus opening the port 39 and relieving the pressure inthe brake-cylinder. It is to be understood, however, that the brakemechanism is not wholly released from the wheels throughout the car orthe train; but this relief mechanism acts to relieve the excessiveapplication of the brakeshoes on the wheels of a particular axle againstwhich the shoes may be applied so forcibly as to skid the wheels andproduce flattened faces on the wheels. The release of the brakemechanism reverses the movement of the rod 44: to

retract the cams from the valve-levers and permit the springs thereof tobecome active in moving the valve-levers out of the path of thetrip-arms; but the trip devices are not returned to their elevatedpositions until the axles become rotative through the motion of thetrain.

It is to be observed that the tripdevices and the levers of therelief-valves are operative in either direction, so that the wellknowncustom of reversing the car end for end does not affect in any way theoperation of my automatic pressure-relief mechanism.

Changes may be made in the form and proportion of some of the partswhile their essential features are retained and the spirit of theinvention is embodied. I do not therefore desire to strictly confinemyself to the precise construction shown, reserving the right to varytherefrom.

In the operation of the brake when the train is standing still the tripdevice is lowered, as heretofore described, while the jointed arm of thevalve-lever is raised in engagement with the cam on the valve-rod. Asthe valve-rod is moved endwise on the application of the brakes the camis held at rest by engagement with the valve arm or lever, the latterbeing confined'at rest by the lowered trip-arm, so that the valve-rodcan slide through the friction-sleeve of one cam.

In making a station stop, in which it is usual to release the brakeswhen the train comes to a standstill, the relief mechanism has no effectwhatever on the brake mechanism because the trip does not descend untilthe wheels are at rest, and a short interval must elapse after the stopbefore the trip descends, during which interval the brakes are released,so that the valve-rod will move the cam to a position where thevalve-lever will be free and will be held by its spring out of the pathof the trip.

' Having thus described the invention, what I claim is- 1. In afluid-pressure railway-brake, the combination with a brake mechanism, ofa relief-valve communicating with an element of said brake mechanism, atrip mechanism driven by a car-axle to normally assume an inoperativeposition relative to the reliefvalve mechanism, and means, controlled bythe brake mechanism to position an element of the relief-valve in thepath of said trip mechanism, said trip mechanism being actuatedautomatically on the stoppage of the car-axle to open the relief-valve,substantially as described.

2. In a fluid-pressure railway-brake, the combination of a brakemechanism, a reliefvalve mechanism communicating with an element of thebrake mechanism, an axle-actufor actuation thereby, and to operate therelief-valve on the stoppageof the car-ax Ie, substantially asdescribed.

3. In an automatic pressure-relief mechanism for fluid-actuated brakes,the combination with a brake mechanism, of a relief-valve communicatingwith an element of the brake mechanism, an axle-actuated trip mechanismnormally held by the rotation of the axle in an inoperative positionwith relation to the valve and adapted to, under certain conditions,assume its operative position without aifecting the relief-valve, andmechanism controlled by the brake to interpose an element of therelief-valve in active relation to the trip mechanism, substantially asdescribed.

4. In a fluid-pressure-actuated brake system for railway-trains, thecombination of a pressure-relief pipe connected with a pressure-chamberof the brake apparatus, a series of reliefvalves for said relief-pipe,said valves having movable operating elements, a series of axle-actuatedindependenttrip mechanisms normally carried by the rotation of thecaraxles out of operative relation to said relief-valve-operatingelements and adapted, when said axles cease to rotate, to actuate saidrelief-valve-operating elements, and means, operated by the brakemechanism, at the period of initial movement thereof, to move saidrelief-valve-operating elements into position for operation by saidaxle-actuated trip mechanisms, substantially as described.

5. In an automatic pressure-relief mechanism for fluid-actuated brakes,the combination of a relief-valve to lessen pressure on a brakemechanism, a trip mechanism normally held by the rotative action of anaxle free from said relief-valve, and means actuated by the brakemechanism and at the period of the application of the brake-shoes tomove an element of the relief-valve in position forengagement by thetrip mechanism, substantially as described.

6. In an automatic pressure-relief mechanism for fluid-actuated brakes,the combination of a normally-closed pressure-relief valve having amovable element, a trip mechanism controlled by the rotative action of acar-axle,

and a valve-positioning device engaging with the movable element of therelief-valve and connected with a part of the brake mechanism topreliminarily position said element of the relief-valve in the path ofthe trip mechanism at the period of the application of the brake,substantially as described.

7. In a fiuid-pressure-actuated brake system for railway-trains, thecombination with a pressure-relief pipe connected with apressure-chamber of the brake apparatus, of a series of relief-valvesfor said relief-pipe, said valves having operating-levers, of a seriesof independent trip mechanisms driven by the train-axles, said tripmechanisms being carried by the rotation of the train-axles out ofoperative relation to the said relief-valve levers, and adapted whensaid axles cease to rotate, to automatically operate said relief- Valvelevers, and means connected to the brake mechanism, and operative at theperiod of initial movement of the brake mechanism, to move saidreliefvalve levers into position for operation by said trip mechanism,substantially as described.

8. In an automatic pressure-relief mechanism for fluid-actuated brakes,a trip mechanism having a counterpoised movable trip geared to acar-axle and capable of an. independent travel in a path around saidaxle on stoppage thereof, in combination with a relief-valve incommunication with a pressurechamber of a brake, and valve-positioningmechanism controlled by a part of the brake, to be interposed in thepath of, and actuated automatically by said counterpoised trip asit'moves independently of the car-axle, substantially as describet 9. Ina fluid-pressure railway-brake, a trip mechanism comprising a casingloosely supported on the caraxle, a counterpoised trip guided in saidcasing to travel around the axle, and gearing between said trip and theaxle for holding the trip in a raised position on the rotation of theaxle and permitting said trip to drop on stoppage of the axle, incombination with a relief-valve in communication with an element of thebrake mechanism, and means actuated by the application of the brake toposition a part of the valve in the path of the trip mechanism,substantially as described.

10. In an automatic pressure-relief mechanism for fluidactuated brakes,a trip mechanism comprising a counterpoised trip, means for guiding saidtrip to travel in a path concentric with the car-axle, and gearingbetween the trip and said axle, in combination with a relief-valve incommunication with a pressure-chamber of the brake, andvalve-positioning devices, substantially as described,

' 11. In an automatic pressure-relief mechanism for fluid-actuatedbrakes, a trip mechanism comprisingacasinghavingaguideway, acounterpoised trip arranged to travel in said guideway and having aspindle, and gearing between said spindle and a can-axle, in combinationwith a relief-valve, and valve-positioning devices, substantially asdescribed.

12. In an automatic pressure-relief mechanism for fluid-actuated brakes,a trip mechanism comprising a casing mounted loosely on an axle, aretainer connected to the casing and guided slidably on a part of acar-truck, and a counterpoised trip geared to an axle, in combinationwith a relief-valve,and val ve-positioning devices, substantially asdescribed.

13. In an automatic pressure-relief mechanism for fluid-actuated brakes,a relief-valve in communication with a pressure-chamber of a brake andhaving a jointed arm, combined with brake-actuated mechanism for movingan element of said arm at the period of the application of the brakemechanism, and a wheel-actuated trip mechanism driven from the car-axletonormally assume an inopera-- tive position during the application ofthe brake and movable automatically on the stoppage of a car-axle toengage the valve-arm and open said relief-valve, as set forth.

14:. In an automatic pressure-relief mechanism for fluid-actuatedbrakes,a relief-valve in communication with a pressure-chamber ofabrake,and a jointed brake-lever in active relation to said valve andhaving a movable arm held bya retractor out of the path of the tripmechanism, in combination with means actuated by a brake to position thevalve-arm at the period of application of said brake,and awheel-actuated trip mechanism,'substantially as described.

15. In an automatic pressure-relief mechanism for fluid-actuated brakes,the combination with a brake-cylinder and its piston, of avalve-actuating rod connected and movable with said piston, africtionally-held cam on said rod, a relief-valve having a yieldable armin the path of said cam, and an axleactuated trip mechanism,substantially as described.

16. In an automatic pressure-relief mechanism for fluid-actuated brakes,the combination with a piston of a brake-cylinder, of a valve-actuatingrod connected operatively with said piston and movable endwise thereby,substantially at the period of the application of the brake mechanism, anormallyelosed relief-valve in communication with the pressure-chamberof said brake, a cam engaged frictionally with said rod and movable alimited distance therewith and disposed in active relation with saidrelief-valve, and Wheel actuated trip mechanism, substantially asdescribed.

17. In an automatic pressure-relief mechanisrn'for fluid-actuatedbrakes, the combination of a valve-actuating rod connected operativelywith an element of the brake mechanism, a normally closed relief-valvein communication with the pressure-chamber of said brake and providedwith a yieldable arm, a cam having frictional engagement with said rodand arranged to actuate the yieldable arm without opening therelief-valve, means for limiting the travel of said cam with thevalverod, and a wheel -actuated trip mechanism arranged to open therelief-valve on the arrestation of an axle, substantially as described.

In testimony that I claim the foregoing as my own I have hereto affixedmy signature in the presence of two witnesses.

SAMUEL L. TERRY.

Witnesses H. T. BERNHERD, M. PERRY HAHN.

